This is a thread for render requests. If you have any questions on how to render, it´s best to make a new thread
But I´ll give you a quick answer here. You just have to select the wheels and apply a different material to the wheel. Look for the diffuse slot in your wheel material in the material editor, that would be the simplest way. That is when you´re using pre-made scenes. If you´re starting from scratch, you will first have to detach the wheel from the tyres.
But if you want to create more metal-like wheels and such there´s more you need to do, especially just experiment.
But for further questions it´s better to start a new thread or ask in existing topics about this
edit: oh and check out the link in my sig named " render tutorial", that could also be of help to you